Remote monitoring of various parameters sensed by instruments within a closed vessel is a common technique. For example, in a nuclear reactor, it is desirable to monitor various parameters, including the reactivity inside the closed reactor vessel. Thus, neutron measuring instruments (and others) are typically disposed within the vessel at various locations and at least portions of the instruments including electrical cabling conventionally extend through ports formed in the bottom of the vessel whereby the signals from the instruments can Be connected to monitors external to the vessel.
Conventionally, the cabling and portions of the instruments hang below the vessel and into a confined and congested work area. Maintenance is typically performed in that area and during scheduled maintenance outages, heavy equipment is also used in this area. Consequently, there is a potential for damaging the cabling and/or portions of the instruments exposed below the vessel. For that reason, protective sleeves have previously been used to protect the cabling and instrument portions depending from the vessel. Such protector sleeves have also been designed to prevent water intrusion into the sleeve that could compromise the electrical integrity of the instrument.
In a previous protective sleeve employed for this purpose, a cylindrical sleeve was provided through which the instrument portion would extend, as well as the electrical cable. A portion of the sleeve, i.e., about 60% was formed of a semi-cylindrical body and semi-cylindrical cover, each having four lugs projecting laterally from each of the body and cover which, when in registry with one another, receive screws whereby the cover and sleeve body may be secured to one another. One end of the cover was received in an annular ring about the protective sleeve. Also, a rectangular gasket was incorporated into the body of the sleeve which, when the cover was secured by the screws to the sleeve body, formed a seal between the cover and body. However, over time, the rectangular sealing gasket was easily damaged and became unbonded relative to the sleeve body. Watertight integrity was lost and essentially the replacement of the gasket required the replacement of the entire sleeve. Importantly, however, the annual maintenance removal and reinstallation of an old protective sleeve cover was not only labor-intensive with that type of construction but also necessarily performed in an area which may be subject to small radiation doses. Typically, the installation of a new protective sleeve cover of this type required an average time of about ten minutes. Because of the potential of radiation exposure, however small and within safe limits, a reduction in the installation time is highly beneficial to minimize any such exposure.